I did a year of factory work. It sucked, that's just my personal opinion. I'm big into fitness, but this was just like putting a big unnecessary strain on my body. My legs, arms, back, hands were always sore, I was breathing in dust all day, and it's miserable being in a place with no windows especially in the summer time. The actual work I could handle it, but the work environment, i'll pass especially for the $12/hr they were paying me.

As for advice, bring plenty of water, get comfortable shoes as people have suggested. Nothing worse than having some crappy uncomfortable shoes that you have to walk around in all day. As was said don't try and re-invent the wheel. And to me, one of the most important things I learned, if something seems unsafe, don't do it. Factory jobs often turn a blind eye to people who do risky maneuvers because they generally are most concerned about production. But the only person who will be affected in the long term if you have a major injury is you.